Construction method for reinforcing a column and reinforcing structure for a column

ABSTRACT

A construction method for reinforcing a column comprises the steps of: disposing a steel plate  3  around the column subjected to reinforcement  10 ; and wrapping a reinforcement sheet  8  impregnated with an adhesive on an outer surface of the steel plate  3 . A sheet impregnated with an adhesive is fabricated in advance such that an amount of adhesive with which the reinforcement sheet  8  is impregnated is 250 g/m2 to 350 g/m2, and the reinforcement sheet is then carried into a construction site. A reinforcing structure of a column comprises: a steel plate  3  disposed around the column  10  subjected to reinforcement; and a reinforcement sheet  8  impregnated with an adhesive, the sheet being wrapped around a plurality of times on an outer surface of the steel plate  3.

TECHNICAL FIELD

The present invention relates to: a construction method for reinforcinga column subjected to reinforcement under a condition with extremelylimited working space and working time, such as the reinforcement of acenter pillar of a subway, a column of an overpass or a parkingstructure, or a column of a building immediately after a disaster; and areinforcing structure.

BACKGROUND ART

Construction for reinforcing a center pillar in a subway tunnel, acolumn of an overpass or a parking structure, a column of a buildingimmediately after a disaster, or the like, takes place under a conditionwith heavily restricted working space and working time.

For example, when reinforcing a center pillar in a subway tunnel, thereinforcement must be implemented in a short period of time at night,outside of operational business hours. Specifically, considering thatcurrent flows in the subway tracks for 30 minutes after the currentsupplied to the tracks is stopped, there are only several daily workinghours at night when the trains are stopped, i.e., a construction time ofabout 3 hours from 1 AM to 4 AM.

In addition, working space is extremely limited, as the space between acenter pillar and a train is narrow. Since the working space that can besecured in a subway tunnel is narrow in this manner, heavy machinery orlarge equipment cannot be used. The same time and spatial limitationsare imposed when reinforcing a column of an overpass or a parkingstructure, or a column of a building site where a disaster has occurred.

Methods for reinforcing a column of a building structure by surroundingthe perimeter of the column with a reinforcing material in order toenhance the earthquake resistance of the column have been proposedheretofore.

For example, Japanese Laid-Open Publication No. 9-177334 (PatentLiterature 1) discloses a construction method for reinforcing a concretecolumn. The method of reinforcement disclosed in Patent Literature 1 isa method comprising: disposing a plurality of steel plates 40 so as tosurround a concrete column 1; overlaying end sections of adjacent steelplates 40 and coupling the end sections with a bolt/nut 41; and fillinga space 42 between the concrete column 1 and the steel plate 40 withgrout as shown in FIG. 12.

Further, Japanese Laid-Open Publication No. 2005-23745 (PatentLiterature 2) also discloses a construction method for reinforcing aconcrete column. The method of reinforcement disclosed in PatentLiterature 2 is a method comprising: disposing steel plates 45 with across-section formed in an L-shape on the four corners of a concretecolumn 1 so as to surround the concrete column 1; binding the steelplates 45 by wrapping a belt-like fiber sheet 46 on the outer perimeterof the steel plates 45; and filling a space 42 between the four steelplates 45 and the concrete column 1 with grout as shown in FIG. 13.

However, the curing period required for grout filled into the spacebetween the concrete column and steel plates to solidify is long inthese construction methods for reinforcement. Thus, the methods ofreinforcement disclosed in these Patent Literatures cannot be employedas a method of reinforcement under a condition where reinforcement workmust be implemented in a short period of time as in the above-describedcase of reinforcing a center pillar of a subway tunnel. In addition,since these methods of reinforcement require the use of injectionequipment for injecting grout into the space between a pillar and asteel plate in a narrow working space, work at a construction site wouldbe extremely difficult.

As a method for reinforcing a column subjected to reinforcement (e.g.,concrete column) without using grout, the inventors investigated amethod comprising disposing a plurality of steel plates in a transversedirection so as to surround the perimeter of a column subjected toreinforcement and wrapping a belt-like fiber sheet thereon whileapplying an adhesive to the outer circumferential surface of the steelplates. Since this method does not use grout, work can be carried outexpeditiously, in addition to the level of earthquake resistance beingequivalent in comparison to a case of using grout (e.g., see Non-PatentLiterature 1: this document studies the level of earthquake resistancecapability of a reinforcing steel plate using mortar, which is alsogrout). However, a fair amount of curing time is required for theapplied adhesive to sufficiently function as an adhesive. For thisreason, it would be difficult to quickly and efficiently completereinforcement work within a limited working time. Even when the amountof adhesive applied was increased to further enhance the adhesiveness,the adhesive dripped down until the adhesive suitably cured, and timeand effort were required to remove the adhesive which dripped down ontothe ground or floor.

CITATION LIST Patent Literature

-   [PTL 1] Japanese Laid-Open Publication No. 9-177334-   [PTL 2] Japanese Laid-Open Publication No. 2005-23745

Non Patent Literature

-   [NPL 1] 51st Annual Conference of the Japan Society of Civil    Engineers, (September 1996), V-529, “EXPERIMENTAL STUDY ON STEEL    BOARD ROLLING REINFORCEMENT FOR RC ELEVATED BRIDGE COLUMN”, p    1056-1057, Central Japan Railway Company member, Hiroshi TAHATA,    Railway Technical Research Institute member, Tsutomu SATO, Railway    Technical Research Institute member, Tadatomo WATANABE, Railway    Technical Research Institute member, Makoto YASUHARA

SUMMARY OF INVENTION Technical Problem

The construction methods for reinforcement in which a belt-like fibersheet is wrapped around steel plates surrounding a column subjected toreinforcement requires wrapping belt-like fiber sheets two or threetimes around the steel plates while applying an adhesive to the steelplates in order to enhance the column strength with the belt-like fibersheets. However, it was found that it was not possible to prevent theadhesive from dripping down from the sheets at the time of application.Accordingly, the amount of adhesive that should have been retained bythe belt-like fiber sheet became insufficient, resulting in insufficientstrength.

For example, in order to impart sufficient strength, it is necessary toprovide 300 g/m² of adhesive for each belt-like fiber sheet. However, itwas found that when a sheet was wrapped around steel plates whileadhesive was applied to the steel plates at a construction site, theadhesive dripped down so that only about 200 g/m² of adhesive wasretained for each belt-like fiber sheet.

In addition, the floor surface of a subway tunnel would be dirtied by anadhesive that drips down from a belt-like fiber sheet, as describedabove, upon application of the adhesive to the belt-like fiber sheet.The dirtied floor surface due to the adhesive would need to be cleaned.However, since construction time is limited as described above, thefloor surface cannot be cleaned.

The present invention has been conceived to solve the above-describedproblem. The objective of the present invention is to provide: aconstruction method for reinforcing a column which enables reinforcementwork on the column subjected to reinforcement in a simple and efficientmanner under a condition with extremely limited working space andworking time; and a reinforcing structure of a column.

Solution to Problem

The present invention has the following features in order to solve theabove-described problem.

A construction method for reinforcing a column according to the presentinvention comprises the steps of: disposing a steel plate around thecolumn subjected to reinforcement; and wrapping a reinforcement sheetimpregnated with an adhesive on an outer surface of the steel plate,thereby achieving the objective described above.

Preferably, a plurality of the steel plates are disposed on the columnsubjected to reinforcement in a vertical direction.

Preferably, the reinforcement sheet is wrapped around the columnsubjected to reinforcement with the steel plate interposed therebetweenin a transverse direction.

Preferably, the steel plate surrounds the column subjected toreinforcement in a form divided into a plurality of steel plates.

Preferably, the reinforcement sheet is wrapped around so that an endsurface, where wrapping ends, of the one reinforcement sheet is at adifferent location in a circumferential direction of the columnsubjected to reinforcement from an end surface, where wrapping ends, ofanother reinforcement sheet adjacent in a vertical direction.

Preferably, an end surface created from dividing the surrounding steelplate overlaps with an end surface of an adjacent divided steel plate ina vertical direction.

Preferably, a sheet impregnated with an adhesive is fabricated inadvance such that an amount of adhesive with which the reinforcementsheet is impregnated is 250 g/m² to 350 g/m², and the reinforcementsheet is then carried into a construction site.

Preferably, the step of applying grout to a wall surface around thecolumn subjected to reinforcement to flatten the wall surface before thestep of disposing the steel plate on the wall surface is furthercomprised.

Preferably, the step of applying grout to a wall surface surrounding thecolumn subjected to reinforcement to flatten the wall surface after thestep of disposing the steel plate on the wall surface is furthercomprised.

A reinforcing structure of a column according to the present inventioncomprises: a steel plate disposed around the column subjected toreinforcement; and a reinforcement sheet impregnated with an adhesive,the sheet being wrapped a plurality of times around an outer surface ofthe steel plate, thereby achieving the objective described above.

Preferably, a plurality of the steel plates are disposed on the columnsubjected to reinforcement in a vertical direction.

Preferably, the reinforcement sheet is wrapped around the columnsubjected to reinforcement with the steel plate interposed therebetweenin a transverse direction.

Preferably, the steel plate surrounds the column subjected toreinforcement in a form divided into a plurality of steel plates.

Preferably, the reinforcement sheet is wrapped around so that an endsurface, where wrapping ends, of the one reinforcement sheet is at adifferent location in a circumferential direction of the columnsubjected to reinforcement from an end surface, where wrapping ends, ofanother reinforcement sheet adjacent in a vertical direction.

Preferably, an end surface created from dividing the surrounding steelplate overlaps with an end surface of an adjacent divided steel plate ina vertical direction.

Preferably, an amount of adhesive with which the reinforcement sheet isimpregnated is 250 g/m² to 350 g/m².

Preferably, grout is applied to a wall surface around the columnsubjected to reinforcement.

Advantageous Effects of Invention

According to the construction methods for reinforcement of the presentinvention, a reinforcement sheet impregnated with an adhesive is wrappedaround the outer surface of a steel plate. Thus, work to wrap a sheetimpregnated with an adhesive around a steel plate can be completed withonly fabricating a sheet impregnated with an adhesive at a factory orthe like and carrying the sheet impregnated with an adhesive to aconstruction site to wrap the sheet around a steel plate at the site.Thus, work to attach a reinforcement sheet to the outer surface of asteel plate with an adhesive at a construction site is unnecessary, sothat the time for applying an adhesive at a construction site can beomitted.

In addition, since adhesive is not applied to the outer surface of asteel plate or a sheet as in the conventional techniques, adhesive doesnot drip down at the construction site to make the floor surface of theconstruction site dirty because the adhesive has reasonably cured toexert a suitable adhesiveness.

Furthermore, since it is possible to impregnate and impart areinforcement sheet with a suitable amount of adhesive, there is no riskof a decrease in strength due to insufficient adhesive. In addition,adhesive would not drip down at the construction site. Accordingly, itis possible to reduce the number of times reinforcement sheets arewrapped around in comparison to a case of applying sheets while applyingan adhesive at a construction site. If anything, strength would not beinsufficient, for example, with a double wrapping of sheets in thepresent invention although conventional construction methods ofreinforcement require triple wrapping.

According to the reinforcing structure of the present invention, thestructure comprises a steel plate disposed around a column subjected toreinforcement and a reinforcement sheet impregnated with an adhesive,which is wrapped a plurality of times around the outer surface of thesteel plate. Thus, a reinforcement sheet in which the adhesive has curedconstrains the column subjected to reinforcement from the outside, withthe steel plate interposed therebetween. Therefore, the earthquakeresistance of a column can be improved.

A columnar surface of a column subjected to reinforcement is notnecessarily formed having a flat surface. For this reason, a steel plateapplied to the columnar surface cannot stably contact the columnarsurface. It is possible to flatten the surface by applying a method,such as applying grout to a columnar surface, such that both surfacesare efficiently in contact.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical schematic cross-sectional view showing the insideof a subway structure.

FIG. 2 is a schematic transverse cross-sectional view of a center pillarportion in a subway structure in one Example of the present invention.

FIG. 3 is a perspective view of a center pillar portion shown in FIG. 2.

FIG. 4 is a diagram for illustrating a construction method forreinforcing the center pillar shown in FIG. 3.

FIG. 5 is a vertical cross-sectional view of an essential part of thecenter pillar shown in FIG. 3.

FIG. 6 is a schematic transverse cross-sectional view of a centerpillar. FIG. 6(a) shows an example of wrapping one layer ofreinforcement sheet around the outer surface of a steel plate in an Lshape. FIG. 6(b) shows an example of wrapping one layer of reinforcementsheet around the outer surface of a steel plate in a U shape. FIG. 6(c)shows an example of wrapping two layers of reinforcement sheets aroundthe outer surface of a steel plate in an L shape.

FIG. 7 is a schematic transverse cross-sectional view of a center pillarportion in a subway structure in yet another Example of the presentinvention.

FIG. 8 is a perspective view of the center pillar portion shown in FIG.7.

FIG. 9 is a schematic transverse cross-sectional view of the centerpillar shown in FIG. 9.

FIG. 10 FIGS. 10(a)-(e) each show a cross-sectional view of variousforms of a coupling portion at the end sections of steel plates.

FIG. 11 is a cross-sectional view of a center pillar in yet anotherExample of the present invention.

FIG. 12 is a cross-sectional view of a conventional reinforcingstructure of a concrete column.

FIG. 13 is a perspective view of another conventional reinforcingstructure of a concrete column.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiments of the present invention are explained indetail while referring to the drawings.

The present invention can be applied to a construction method forreinforcing a column subjected to reinforcement, such as reinforcing acenter pillar of a subway tunnel, a column of an overpass or a parkingstructure, or a column of a building immediately after a disaster, underconditions with extremely limited working space and working time.

A column subjected to reinforcement as referred herein includesreinforced concrete columns, steel framed reinforced concrete columns,concrete filled steel tube columns, and steel columns.

Hereinafter, a column reinforcing method for reinforcing a concretecenter pillar in a subway tunnel and a column reinforcing structure areexplained as examples of embodiments of the present invention.

Embodiment 1

FIG. 1 is a schematic vertical cross-sectional view of a subwaystructure (inside a subway tunnel), FIG. 2 is a schematic transversecross-sectional view of a center pillar portion in the subway structure,and FIG. 3 is a perspective view of the center pillar portion thereof.

As shown in FIGS. 1-3, for example, a plurality of center pillars 10 areerected on a bottom floor board 12 for dividing a train track (railway)in one direction and a train track (railway) in the opposite direction14 at predetermined intervals along the railways in a subway structure.

The center pillars 10 are formed such that the transverse cross-sectionhas, for example, a square shape. A steel plate 3 is disposed around thecenter pillar 10 so as to surround the center pillar 10. One or aplurality of steel plates 3 can be disposed on the center pillar 10 inthe vertical direction (upright direction). Further, the steel plate 3can surround the center pillar 10 with one plate or in a form dividedinto a plurality of plates. In this Embodiment, for example, four steelplates 3 (the number of steel plates is not represented in the drawingas the plates are hidden by the reinforcement sheet) are disposed tosurround the center pillar 10.

For example, a relatively thin steel plate with a thickness of about 1.6mm is used as the steel plate 3. The periphery of a column subjected toreinforcement may be directly covered with a single steel plate.However, a steel plate formed by dividing the plate into a plurality ofplates and bending the plates to give an L-shaped transverse crosssection can also be used. The plate-like section on one side and theplate-like section on the other side, with a corner section of the steelplate 3 formed into an L-shape therebetween, may have the same ordifferent lengths. Since such a thin steel plate 3 is light, the steelplate 3 can be carried by hand to a construction site in a subwaystructure without the use of heavy machinery.

As shown in FIG. 4(a), each steel plate 3 is disposed to surround acorner section of the center pillar 10. An end surface created bydividing the surrounding steel plate 3 overlaps with an end surface ofthe adjacent divided steel plate 3 in the vertical direction. That is,an end section of each divided steel plate 3 surrounding the centerpillar 10 extends along the wall surface of the center pillar 10 and endsections thereof overlap on the wall surface. In this manner, an endsection of one of the divided steel plates 3 overlaps an end section ofthe other, adjacent divided steel plate 3 in the transverse direction(in the circumferential direction around the center pillar).

As shown in FIG. 5, the steel plate 3 is disposed on the outer side ofthe center pillar 10 such that at least a portion of the inner surfaceof the steel plate 3 contacts the outer surface of the center pillar 10.

Next, a reinforcement sheet 8 impregnated with an adhesive is wrappedaround the outer surface of the steel plate 3. Naturally, the sheet 8can be wrapped around the outer surface of the adjacent steel plate 3 inthe columnar vertical direction while extending out from the outersurface of the steel plate 3.

The reinforcement sheet 8 is an adhesive-impregnated fiber sheet havingnumerous fibers.

Fibers that can be used in a fiber sheet include carbon fiber, glassfiber, aramid fiber, polyethylene fiber, and vinyl on fiber. Thesefibers can be used individually or as a combination of multiple types offibers. Aramid fibers are preferable in terms of price and in terms ofhaving excellent properties such as tensile strength. A fiber sheet canbe used in a single-layer form or in a two or more layer form.

In order to impregnate such a fiber sheet with an adhesive, the adhesivecan be applied to a fiber sheet with a brush or a roller in a factory.Alternatively, the fiber sheet can be impregnated with adhesive byimmersing the sheet in a container containing the adhesive in a factory.A sheet can be impregnated with a desired amount of adhesive inaccordance with such methods of adhesive impregnation. Further, whensheets are impregnated with an adhesive in a factory, the sheets can beimpregnated with nearly a constant amount of adhesive. Specifically,since the temperature in a factory is almost constant, the viscosity ofthe adhesive would be constant regardless of the season. For thisreason, the amount of adhesive a sheet is impregnated with would notvary significantly depending on the season.

The type of adhesive for impregnating a fiber sheet is not limited, butuse of an adhesive such as an epoxy adhesive, methacrylic adhesive, oracrylic adhesive is preferable.

Adhesives that cure at normal temperature are particularly preferable. Atwo-component type adhesive, which is an adhesive that starts curing bymixing a main agent with a curing agent that are both made of syntheticchemical components, and a one-part type adhesive can both be used.However, use of a two-component type adhesive is preferable for thereare generally more two-component type adhesives with higher adhesivestrength, or, that is to say, two-component type adhesives are morereliable with respect to securing a predetermined adhesive strength.

The amount of adhesive with which a fiber sheet is impregnated ispreferably 250 g/m² to 350 g/m², more preferably 280 g/m² to 330 g/m²,and particularly preferably 290 g/m² to 310 g/m².

When the amount of impregnating adhesive is much less than 250 g/m², thestrength of adhesion of the reinforcement sheet 8 to the steel plate 3tends to decrease. Even if the amount of adhesive impregnated exceeded350 g/m², the adhesive strength would not increase much. However, theweight would increase and the material cost would be higher.

In this manner, the reinforcement sheet 8 is fabricated by impregnatinga fiber sheet in advance with a predetermined amount of adhesive in afactory. The adhesive is reasonably cured to come to have a strongadhesive capability. The time required for reasonable curing thereof is2 to 3 hours based on outside air temperature of 20° C. The viscosity ofadhesives differs depending on the type and manufacturer of theadhesive. For this reason, manufactures have prepared adhesives with twotypes of viscosity, i.e., for summer and for winter. Thus, an adhesivewith a suitable viscosity can be used.

The sheet impregnated with an adhesive (reinforcement sheet) 8 iscarried into an implementation site. The reinforcement sheet 8 is thenwrapped around the outer surface of the steel plate 3 disposed aroundthe center pillar 10.

The reinforcement sheet 8 may be wrapped around the center pillar 10with the steel plate 3 interposed therebetween in a slightly slantedstate. However, the reinforcement sheet 8 is generally wrapped aroundthe center pillar 10 with the steel plate 3 interposed therebetween inthe transverse direction (horizontal direction). That is, one or aplurality of reinforcement sheets 8 are wrapped around the columnarsurface with the steel plate 3 interposed therebetween such that thelongitudinal direction of fibers included in the reinforcement sheet 8almost matches the circumferential direction of the center pillar 10(direction orthogonal to the axial direction of the center pillar).

It is preferable that an end surface, where wrapping ends, of onereinforcement sheet 8 wrapped around the center pillar 10 overlaps anend surface, where wrapping begins, of the reinforcement sheet 8.

As shown in FIG. 4(b), when a plurality of reinforcement sheets 8 arewrapped around the perimeter of the center pillar 10, the plurality ofreinforcement sheets 8, 8 are wrapped around the perimeter of the centerpillar 10 such that end sections of adjacent reinforcement sheets 8overlap each other. For example, as shown in FIG. 6(a), a firstreinforcement sheet 8 a is wrapped around the columnar surface with thesteel plate 3 interposed therebetween, and then a second reinforcementsheet 8 b adjacent to the first reinforcement sheet 8 is wrapped aroundthe columnar surface with the steel plate 3 interposed therebetween suchthat an end section of the second reinforcement sheet 8 b overlaps anend section of the first reinforcement sheet 8 a.

The shape and size of the reinforcement sheet 8 is not limited. Forexample, a belt-shaped reinforcement sheet or a rectangularreinforcement sheet can be used.

The length of the reinforcement sheet 8 in the circumferential directionof the central pillar 10 can be appropriately set in accordance with thelength of the perimeter of the central pillar 10. For example, thelength of the reinforcement sheet 8 can be greater than or equal to thewidth of the center pillar 10. The reinforcement sheet 8 wrapped arounda columnar surface with the steel plate 3 interposed therebetween ispreferably wrapped around in a form with an L-shape transversecross-section (FIG. 6(a)) or a U-shape transverse cross-section (FIG.6(b)). The reinforcement sheet 8 is preferably wrapped around the outersurface of the steel plate 3 so as to span across a first steel plate 3and a second steel plate 3 that are adjacent in the circumferentialdirection of the center pillar 10 from the viewpoint of strength. Thewidth in the vertical direction (upright direction of the center pillar)of the reinforcement sheet 8 is determined while taking intoconsideration the ease of handling of a reinforcement sheet or the like.The width may be of any size as long as the reinforcement sheet 8 can bereadily transported.

After the reinforcement sheet 8 is wrapped around the columnar surfacewith the steel plate 3 interposed therebetween, an adhesive with whichthe reinforcement sheet 8 is impregnated cures. Thus, the plurality ofreinforcement sheets 8 are integrated, so that the reinforcement sheets8 are secured to the center pillar 10 with a plurality of the steelplates 3 interposed therebetween.

As shown in FIGS. 3 and 4(b), when a plurality of the reinforcementsheets 8 are wrapped around the center pillar 10 in the verticaldirection (upright direction), the reinforcement sheet 8 is wrappedaround so that an end surface, where wrapping ends, of one reinforcementsheet 8 would be at a different location from an end surface of anotherreinforcement sheet 8 adjacent in the vertical direction. Thus, anoverlapping section of end sections of one reinforcement sheet 8positioned on the top side of the center pillar 10 is different in thecircumferential direction of the center pillar 10 from an overlappingsection of end sections of the reinforcement sheet 8 positioned adjacentin the lower side of said reinforcement sheet 8. This is a matter ofcourse in terms of effectively imparting strength.

As shown in FIGS. 4(b), 6(a), and 6(b), the reinforcement sheet 8 may bewrapped around in one layer, or as shown in FIG. 6(c), the reinforcementsheet 8 may be wrapped around in two layers. Indeed, the reinforcementsheet 8 may be wrapped around in more layers.

When the reinforcement sheet 8 is wrapped around the columnar surfacewith the steel plate 3 interposed therebetween in two layers, a secondlayer of reinforcement sheet 8 (top layer of reinforcement sheet) iswrapped on top of a first layer of reinforcement sheet 8 (lower layer ofreinforcement sheet). It is preferable that the second layer ofreinforcement sheet 8 is wrapped on top of the first reinforcement sheet8 such that an overlapping section 81 of adjacent first layerreinforcement sheets 8 and an overlapping section 82 of adjacent secondlayer reinforcement sheets 8 are offset in the circumferential directionof the center pillar 10.

In this manner, the overlapping sections 81 and 82 of reinforcementsheets 8 are offset in the circumferential direction of the centerpillar 10 so that the thickness of the reinforcement sheet 8 over theentire circumference is nearly the same and the strength thereof isuniform.

The reinforcement sheet 8 may be temporarily secured while thereinforcement sheet 8 is pressed onto the outer surface of the steelplate 3 by using a pressing jig for pressing the sheet 8 from theoutside.

It is possible to apply exterior finishing, such as painting, finishingmortar, or tiling, on the outer surface of a reinforcement sheet 8 thathas been wrapped around as needed.

For the reinforcement sheet 8, a fiber sheet is impregnated with apredetermined amount of adhesive in advance, and the sheet would not beimpregnated with an adhesive at a construction site. Thus, thereinforcement sheet 8 has excellent workability. In addition, since theadhesive is in a semi-cured state such that the adhesive does not dripdown from the fiber sheet when the reinforcement sheet 8 is carried, theadhesive would not dirty the floor surface by dripping down from thesteel plate 3 or the reinforcement sheet 8 when applied.

As shown in FIG. 5, when there is unevenness on the surface of thecenter pillar 10, the inner surface of the steel plate 3 contacts onlythe protruding sections on the surface of the center pillar 10 when thesteel plate 3 is disposed on the outer surface of the center pillar 10.Thus, a gap 11 is created between the outer surface of the center pillar10 and the steel plate 3. In order to enhance the reinforcing functionof the reinforcement sheet 8, grout 6 is applied to the gap 11 createdbetween the center pillar 10 and the steel plate 3 to allow the wallsurface of the center pillar 10 to contact the steel plate surface athigh efficiency. With such application, the surface of the center pillar10 becomes flat and the steel plate 3 is stably disposed on the centerpillar 10, whereby the reinforcing function of the reinforcement sheet 8is enhanced.

The grout 6 is applied to the surface of the center pillar 10 orinjected into the gap 11 created between the center pillar 10 and thesteel plate 3 before or after disposing the steel plate 3 around thecenter pillar 10.

When the grout 6 is applied to the surface of the center pillar 10before disposing the steel plate 3 around the center pillar 10, a toolsuch as a brush or trowel may be used to apply the grout 6 to thesurface of the center pillar 10. In order to fill the gap 11 between thecenter pillar 10 and the steel plate 3 with the grout 6, the grout 6 isinjected from a hole opened in the steel plate 3. Upon injection, thesteel plate 3 is temporarily secured to the center pillar 10 with a pinor the like to hold the steel plate 3 to the center pillar 10.

In such a construction method for reinforcing the center pillar 10, theentire circumference of the center pillar 10 is surrounded by aplurality of steel plates 3, 3, and a plurality of reinforcement sheets8 are applied to the columnar surface with the plurality of steel plates3, 3 interposed therebetween by an adhesive impregnated in advance. Theplurality of reinforcement sheets 8 are integrated in a state where theadhesive is solidified. Accordingly, since the reinforcement sheet 8constrains the movement of the entire center pillar 10 via the steelplate 3, the earthquake resistance of the center pillar 10 can beenhanced.

The plurality of steel plates 3 are secured to the center pillar 10 bythe reinforcement sheet 8. Thus, there is no need for welding the steelplates 3 together or coupling the plates with a coupling tool. Hence,the steel plate 3 is readily secured to a column.

Further, the reinforcement sheet 8 has a predetermined dimension. Thus,the reinforcement sheet can be readily transported to a constructionsite. The reinforcement sheet 8 is impregnated with an adhesive.Further, work to wrap the reinforcement sheet 8 onto a column is simpleand the adhesive would not drip down from the sheet upon wrapping.

The reinforcement sheet 8 is wrapped around a columnar surface with thesteel plate 3 interposed therebetween. Thus, even if the surface of acolumn has unevenness, the outward appearance of the reinforcement sheet8 would be flat so the aesthetics would not be ruined.

In the above-described Embodiment, four steel plates were disposedaround a column subjected to reinforcement in the vertical direction ofthe column subjected to reinforcement. However, the number of steelplates disposed around a column is not limited thereto. One or two ormore steel plates can be disposed around a column. It is preferable thata steel plate is divided into two or more plates for use to be able toadapt to columns with different sizes. Furthermore, the transversecross-sectional shape created upon dividing the steel plate is notlimited to an L-shape. A steel plate with a U-shaped transversecross-sectional shape can also be used.

Embodiment 2

In the above-described Embodiment 1, a plurality of steel plates weredisposed around the center pillar 10 such that an end surface createdfrom dividing a surrounding steel plate overlaps with an end surface ofan adjacent divided steel plate in the vertical direction. However, inEmbodiment 2, a plurality of steel plates 3 are disposed around a centerpillar 10 by coupling end sections of adjacent steel plates 3, 3 witheach other with a fastener 16.

The details thereof are as follows.

As shown in FIGS. 7-9, two steel plates 3, 3 are disposed around thecenter pillar 10 with, for example, a square shape transversecross-section so as to surround the center pillar 10.

Steel plates that are formed by bending a relatively thin steel platewith a thickness of about 1.6 mm in a U-shaped transverse cross-sectioncan be used as the steel plate 3.

A coupling section 4 for coupling a pair of steel plates 3 to each otheris formed at both ends of the steel plate 3. In this embodiment, thecoupling section 4 is formed by bending both ends of the steel plate 3outward as shown in FIGS. 9 and 10(a). One or more throughholes forallowing a fastener 16 such as a screw or a bolt may be formed on thecoupling section 4. As shown in FIG. 10, the coupling section 4 providedon the end section of the steel plate 3 is formed to be long in theupright direction of the center pillar 10.

Next, a reinforcement sheet 8 impregnated with an adhesive with apredetermined length is pressed onto the outer surface of the steelplate 3 to apply the reinforcement sheet 8 to the outer surface of thesteel plate 3.

The reinforcement sheet 8 is a belt-like fiber sheet consisting ofnumerous long fibers extending in one direction, which is impregnatedwith an adhesive.

The sheet impregnated with an adhesive (reinforcement sheet) 8 iscarried into an implementation site. The reinforcement sheet 8 is thenapplied to the outer surface of the steel plate 3 disposed around thecenter pillar 10.

The end sections of adjacent steel plates 3, 3 are then coupled to eachother. It is sufficient for the coupling thereof to bring together eachof the coupling sections 4, 4 formed on the end sections of the adjacentsteel plates 3, 3 and couple both of the coupling sections 4, 4 with thefastener 16 such as a screw or a bolt/nut.

When coupling the end sections of steel plates 3 to each other, as shownin FIG. 9 and FIG. 10(a), the end section of the reinforcement sheet 8may be extended up to the end section of the steel plate 3, and the endsection of the reinforcement sheet 8 may be secured to the end sectionof the steel plate 3 while coupling the pair of steel plates 3, 3 withthe fastener 16.

Furthermore, as shown in FIG. 10(b), the end sections of adjacent steelplates 3, 3 may be directly coupled to each other with the fastener 16.In this case, the end section of the sheet 8 does not extend up to theend section of the steel plate 3. The end section of the reinforcementsheet 8 is secured to the end section of the steel plate 3 with afastener 18 in a separate process from the work to couple the pair ofsteel plates 3, 3 with the fastener 16.

As shown in FIG. 10(c), a washer plate 17 that is long in the up anddown directions may be provided on the outside of the reinforcementsheet 8, and the end section of the steel plate 3 and the end section ofthe sheet 8 may be coupled with the fastener 16 so as to hold down thereinforcement sheet 8 with the washer plate 17.

Furthermore, as shown in FIG. 10(d) and FIG. 10(e), the coupling may beconfigured such that each of the end sections of adjacent steel plates3, 3 extends towards the opposite direction from each other, and thesteel plates 3, 3 and the sheets 8, 8 are coupled by the fastener 16while stacking the end sections of the steel plates 3, 3 and sheets 8,8. The embodiment shown in FIG. 10(e) is configured such that the endsection of one of the steel plates 3 is bent to form a step section 20so that the end section of the other steel plate 3 can be inserted inthe step section 20. Further, in this example, a large hole into which abolt head can be inserted and a small long slotted hole in communicationwith the large hole are formed on the steel plate 3 disposed inside. Thebolt head is passed through the large hole and the bolt is then shiftedalong the long slotted hole to pass the bolt base section through thethrough hole of the steel plate 3 on the outside.

Further, in the Embodiments shown in FIG. 10(d) and FIG. 10(e), a holefor allowing a fastener 16 such as a bolt to pass through is formed as along slotted hole. The steel plates 3, 3 secured with the fastener 16are enabled to slide and move within the long slotted hole to be able tohandle a wider range of shaking of a column due to vibrations.

Examples of forms of the reinforcement sheet 8 applied to the steelplate 3 includes the following.

For the reinforcement sheet 8, a plurality of sheets 8 with apredetermined width and a predetermined length that is long in thehorizontal direction (direction of fibers is along the longitudinaldirection of the sheet) may be prepared and applied to the outer surfaceof the steel plate 3 so that there are a plurality of rows at the topand bottom. Alternatively, the sheet 8 that is long in the verticaldirection with a predetermined length may be applied to the entireoutside surface of the steel plate 3. The reinforcement sheet 8 may beapplied to the outside surface of the steel plate 3 in a single layer orin two or more layers.

In such a construction method for reinforcing the center pillar 10, theentire circumference of the center pillar 10 is surrounded by aplurality of steel plates 3, 3 and the end sections of the steel plates3, 3 are coupled to each other. Furthermore, the steel plates 3surrounding the center pillar 10 are surrounded by the reinforcementsheets 8, 8, and the end sections of the reinforcement sheet 8 arecoupled to each other via the end sections of the steel plates 3.Accordingly, since the center pillar 10 is reinforced with the steelplate 3 and the reinforcement sheet 8, the rigidity of the steel plate 3and the property of the reinforcement sheet 8 are imparted thereto. As aresult, the earthquake resistance of the center pillar 10 can beenhanced.

As shown in FIG. 11, the configuration may be such that four steelplates 3 with an L-shaped cross section are each disposed at a cornersection of a center pillar 10, and coupling sections 4 provided on bothend sections of each steel plate 3 are in contact with coupling sections4 of an adjacent steel plate 3. The coupling sections 4, 4 are coupledwith a fastener 16. In Embodiment 2, the weight of the steel plate 3 isfurther reduced to further facilitate carrying of the steel plate 3 to aconstruction site.

In the above-described Embodiment, an example of fabricating a sheetimpregnated with an adhesive at a factory and applying the sheet on theouter surface of a steel plate at a construction site has been shown.However, it is also possible to apply a sheet impregnated with anadhesive on the outer surface of a steel plate at a factory to fabricatea composite material in which the steel plate and the sheet impregnatedwith an adhesive are laminated, and to carry the composite material intoa construction site and couple the material to the perimeter of acolumn.

In the above-described Embodiments, a center pillar of a subway has beenexplained as the column subjected to reinforcement. However, the presentinvention is not limited to center pillars. In addition to reinforcementof a center pillar of a subway, the present invention can be optimallyimplemented for reinforcing, for example, columns for an overpass,parking structure, building or a column immediately after a disaster.

In the above-described Embodiments, the cross-sectional shape of acenter pillar is square. However, the present invention is applicableeven if the center pillar is a polygonal column other than a squarecolumn (e.g., octagonal column, hexagonal column etc.), cylindricalcolumn or the like. In this case, a steel plate is formed into a shapeconforming to the external shape of a column. It is also possible todivide a steel plate into a plurality of upper and lower pieces andcouple the upper and lower plate pieces to install each of the dividedsteel plate pieces around a column.

INDUSTRIAL APPLICABILITY

The present invention provides: a construction method for reinforcing acolumn subjected to reinforcement under a condition where reinforcementof a column subjected to reinforcement, such as a center pillar of asubway tunnel, a support column of an overpass or parking structure, ora column of a building immediately after a disaster, must be implementedin a short period of time; and a reinforcing structure.

REFERENCE SIGNS LIST

-   3 Steel plate-   8 Reinforcement sheet-   10 Center pillar

The invention claimed is:
 1. A construction method for reinforcing acolumn, comprising the steps of: disposing a steel plate around thecolumn subjected to reinforcement, the steel plate being disposed suchthat the steel plate surrounds the column subjected to reinforcement andat least a portion of an inner surface of the steel plate contacts anouter surface of the column subjected to reinforcement; wrapping areinforcement sheet impregnated with an adhesive on an outer surface ofthe steel plate, wherein the portion of the steel plate having the innersurface thereof in contact with the outer surface of the columnsubjected to reinforcement also has the reinforcement sheet wrapped onthe outer surface thereof; and securing the reinforcement sheet to thesteel plate by curing the adhesive impregnated into the reinforcementsheet.
 2. The construction method for reinforcing a column of claim 1,wherein a plurality of the steel plates are disposed on the columnsubjected to reinforcement in a vertical direction.
 3. The constructionmethod for reinforcing a column of claim 1, wherein the reinforcementsheet is wrapped around the column subjected to reinforcement with thesteel plate interposed therebetween in a transverse direction.
 4. Theconstruction method for reinforcing a column of claim 1, wherein thesteel plate surrounds the column subjected to reinforcement in a formdivided into a plurality of steel plates.
 5. The construction method forreinforcing a column of claim 1, wherein the reinforcement sheet andanother reinforcement sheet adjacent to the reinforcement sheet in avertical direction are wrapped around the column subjected toreinforcement, so that an end surface of the reinforcement sheet is at adifferent location from an end surface of the another reinforcementsheet adjacent in the vertical direction in a circumferential directionof the column subjected to reinforcement, wherein the wrapping of thereinforcement sheet ends at the end surface of the reinforcement sheet,and wherein the wrapping of the another reinforcement sheet ends at theend surface of the another reinforcement sheet.
 6. The constructionmethod for reinforcing a column of claim 4, wherein an end surfacecreated from dividing the surrounding steel plate overlaps with an endsurface of an adjacent divided steel plate in a vertical direction. 7.The construction method for reinforcing a column of claim 1, wherein asheet impregnated with an adhesive is fabricated in advance such that anamount of adhesive with which the reinforcement sheet is impregnated is250 g/m² to 350 g/m², and the reinforcement sheet is then carried into aconstruction site.
 8. The construction method for reinforcing a columnof claim 1, further comprising the step of applying grout to a wallsurface around the column subjected to reinforcement to flatten the wallsurface before the step of disposing the steel plate on the wallsurface.
 9. The construction method for reinforcing a column of claim 1,further comprising the step of applying grout to a wall surfacesurrounding the column subjected to reinforcement to flatten the wallsurface after the step of disposing the steel plate on the wall surface.